The invention relates to a textile web, especially a textile-covered web for a paper-making machine, which, viewed from a transverse direction, is provided with several web sections that extend parallel to one another in a lengthwise direction and are aligned adjacent to one another, with their lateral edges being attached to one another via fasteners.
Textile webs of the type described above are used primarily to transport paper webs through a paper-making machine (GB-A-975 750; EP-B-0 464 258; U.S. Pat. No. 5,360, 656). They are comprised of web sections extending lengthwise across the web, with the width of the sections being considerably narrower than the actual width of the textile web. The web sections extend primarily in a lengthwise direction along the textile web, sometimes at a slight angle to it. The textile web is thus designed such that one or more strips of textile are progressively wound in a lengthwise direction to the textile web, and spirally, crosswise to it.
The web sections may be comprised of structural fibers, for example in the form of a woven fabric. The structural fibers may, however, also form a support base, to which a carded fibre batt tissue is needle-punched on one or both sides, so that the final textile web forms a felt. Such felts are suited especially for use in guiding the paper web in the pressing section of a paper-making machine.
With known textile webs of this type, the individual web sections do not overlap one another, they actually push up against one another along their lateral edges. In such cases, in order to ensure adequate lateral stability, the lateral edges are connected to one another. In the abovementioned documents, it is, therefore, proposed that the lateral edges be sewn together via a zigzag stitch, that they be fused or welded, for example, by ultrasonic welding. As an alternative, the above mentioned documents propose that the lateral edges be provided with seam loops and the connection be made via a wire pushed through the seam loops.
In EP-0 947 623, a connection for the web sections is proposed, which consists of cross thread sections that project beyond the lateral edges of the web sections and overlap, interlocking with one another, and of a joining thread that is bonded to these sections. The establishment of such a connection is not without problems, however, and difficulties arise in matching the porosity of the area around the lateral edges to the porosity of the remaining areas of the web sections. In a paper-making machine it is important, however, that the porosity of the textile web be even over the entire width of the web. A further requirement is that the connection of the web sections one over the other be as firm as possible both in a crosswise and in a lengthwise direction.
The object of the present invention is to design a method for connecting the lateral edges of the web sections in a textile web of the type described at the beginning, such that it is easier to produce and possesses a high degree of stability, but its porosity does not deviate substantially from the porosity of other areas of the textile web.
This object is attained in accordance with the invention in that the adjacent lateral edges of the web sections follow a meandering course, with alternating projections and recesses, and the web sections are interlocked with one another via these projections and recesses, and in that the fasteners connect the projections to one another, in that they extend preferably in a lengthwise direction and are designed to be continuous, to the greatest extent possible.
Thus, the basic premise of the invention is that the lateral edges of the web sections are not straightxe2x80x94as in the current state of the artxe2x80x94but meander, with interlocking projections and recesses, as with toothed gears, and the connection of the adjacent web sections is accomplished via the fasteners used to connect the projections. This type of connection is relatively simple in comparison with known types of connections, and can be machine-produced. It has been found that a connection that is very firm both in a lengthwise and in a crosswise direction can be produced, without the porosity of the area around the lateral edges of the textile web deviating substantially from the porosity of other areas.
The fasteners may be designed, for example, as sewn seams, which preferably extend parallel to the lengthwise direction of the web sections, with several parallel sewn seams being provided per connection. Instead of, or in combination with, such sewn seams, sections of adhesive tape may be used, which cover the area of the projections and recesses partially or, preferably, completely, and may even extend beyond this area. In special cases, the sections of adhesive tape may contain heat-bonding adhesive, or be composed thereof. The heat-bonding adhesive may be activated via heat and pressure once the sections of adhesive tape have been put in place. In order to keep the porosity in this area from being substantially reduced, the sections of adhesive tape should be designed to be porous, in other words they should contain holes, which will ensure sufficient open crosswise surface area.
The sections of adhesive tape may be designed in many different ways. For instance, bonding sheets provided with an adhesive coating may be used, wherein the adhesive coating may consist of a suitable adhesive, such as the above mentioned heat-bonding adhesive. In order to ensure adequate porosity, the bonding sheets should be perforated.
Instead of the above, or in combination with it, the sections of adhesive tape may also be designed as spunbonded tissue, preferably equipped with heat-bonding adhesive fibers. The advantage of using such sections of adhesive tape is that they can be cut to fit, such that they will not seriously affect the porosity of the area in question, and such that their structure will correspond to the structure of the other areas. By activating the heat-bonding fibers via heat and pressure, a firm connection between the interlocking projections is produced. The heat-bonding fibers may consist entirely of heat bonding adhesive, in which case it is advantageous for them to be present only proportionally in the non-woven tissue that forms the section of adhesive tape. They may, however, also be designed as bicomponent fibers, in which heat-bonding adhesive is proportionally present.
Regarding the meandering design of the lateral edges, various shapes are possible, for example wave-type or zigzag shapes. The projections, however, may also be trapezoidal or rectangular in shape. Other shapes for the lateral edges are also possible.
The web sections may be provided with a support base, as is known in the art, or may even be composed thereof, wherein the support base takes up the lengthwise and crosswise forces that act upon the textile web. To the extent that the textile web is to be designed as a felt, such as a press felt designed specifically for use in the pressing section of a paper-making machine, the supports may be needle-punched with spunbonded tissues, so that a felt-like surface is formed on both sides.
Suitable support bases include woven fabrics, knitted fabrics, or even reinforced spunbonded tissues, wherein the woven fabrics, knitted fabrics or spunbonded tissues are used in several layers, and may even be used in combination with one another.
Synthetic nettingxe2x80x94in single or multiple layers, alone or in combination with the above mentioned types of support basesxe2x80x94may also be provided, as is described, for example, in EP-B-0 285 376, EP-A-0 307 182, WO 91/02642, or WO 92/17643. The advantage of synthetic netting is that it will edges, and thus offers a firm hold on the fasteners that extend over the projections. For this reason it is immaterial whether the individual webs of synthetic netting extend in a lengthwise or crosswise direction, or run diagonally. The synthetic netting may be produced as described in the above-named documents. One particularly efficient method for producing synthetic netting of this type consists in using extrusion technology, as is described, for example, in U.S. Pat. Nos. 4,123,491, 3,917,889, and 3,767,353.
The width of the area comprising the projections and recesses may be determined in accordance with given stability requirements. Advantageously, an area of up to 50 cm in width is suitable, with areas ranging from 10 to 20 cm being preferred.